Re: Tubing Notcher

Gary,

Torch is aligned radially to the pipe. Rotation and linear movement
of the pipe relative to the torch define the position on the pipe
which is being cut.

The cutting angle will need to change in two dimensions to obtain
the appropriate angle for the cut relative to the pipe. ie., the
torch angle must change both relative to the length of the pipe and
in the transverse direction. Consequently, surely 2 rotational axis
are required to control the torch?

At the point of the cut furthest from the end of the pipe, the torch
will be angled along the length of the pipe whereas at other cutting
positions, the torch must be angled across the length of the pipe.
In the general position of cut, the torch would be angled in both
planes.

The same would apply to implement a standard plasma cutting machine
for flat plate with a bevel cutting feature. For a rectangular
plate, whilst cutting in the x direction the torch would have to
rotate in the plane of the y-axis and when cutting a side of the
plate in the y direction the torch would have to rotate in the plane
of the x-axis. Again, two rotational motions would be required to
control the torch angle.

Is there some flaw in my logic and/ or a special trick that you used
in your machine to control the torch angle with just one rotational
movement?

I shall look into pipe threaders. Such a machine would seem to
provide a good solution for holding the workpiece.

It is interesting that pipe threaders seem to generally work on the
principle of rotating the pipe rather than the cutter albeit that
the pipe is relatively heavy.

Douglas

--- In CAD_CAM_EDM_DRO@yahoogroups.com, gary <garyclick1@c...> wrote:
>
> The tube ends are beveled in addition to being notched to create
a
> welding preparation for welding from the outside. Since the
outside is
> cut away for the bevel the intersecting surface remaining is the
sharp
> edge of the inside of the tube. To generate the welding bevel the
second
> rotary axis tilts the torch +/-75 degrees, if the center of the
pivot to
> tilt the torch is not aligned to the tube ID, tilting the torch
will
> increase or decrease the length of the tube making the notch
inaccurate.
>
> As far as the rotation of the torch is concerned in more than one
plane,
> remember we were notching the end of the tube and the tube was
being
> rotated. The torch centerline was aligned with a radial element of
the
> tube centerline. The notch or "fishmouth" was generated by
rotating the
> tube around its axis and moving the torch along a linear axis
parallel
> to the tube centerline. The tube was mounted in a large hollow
chuck
> stolen from a very large Landis pipe threading machine.
>
> gary